### An item granting four damage resistances is an extremely powerful item. 

[Upper_Case's answer](https://rpg.stackexchange.com/a/188884/62294) has all you really need to come to a ruling here, but I think we can motivate that answer further by comparing the proposed item to existing magic items and magic item guidance. There are already two magic items that grant damage resistance, the Ring of Resistance and Armor of Resistance, and these each grant *a single damage resistance*, and are "Rare" magic items, valued at 501 - 5,000 gp. If damage resistance were as simple as following some mundane design principles with mundane materials, we wouldn't have magic items filling the same role that cost astronomically more than a warm coat. 

An item granting four damage resistances is possible, but only under extremely unlikely circumstances. It is possible under written guidance, for a DM to create a magic item that does exactly as you describe, granting four damage resistances, and that is by creating *an Artifact*:

>An artifact is a unique magic item of tremendous power, with its own origin and history. An artifact might have been created by gods or mortals of awesome power. It could have been created in the midst of a crisis that threatened a kingdom, a world, or the entire multiverse, and carry the weight of that pivotal moment in history.
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>Characters don’t typically find artifacts in the normal course of adventuring. In fact, artifacts only appear when you want them to, for they are as much plot devices as magic items. Tracking down and recovering an artifact is often the main goal of an adventure. Characters must chase down rumors, undergo significant trials, and venture into dangerous, half-forgotten places to find the artifact they seek. Alternatively, a major villain might already have the artifact. Obtaining and destroying the artifact could be the only way to ensure that its power can’t be used for evil.

Artifacts represent the most powerful magic items ever created, and are totally unique. When introducing an atifact into the campaign, the *Dungeon Master's Guide* suggests assigning some random properties to the item:

>An artifact can have as many as four minor beneficial properties and two major beneficial properties. It can have as many as four minor detrimental properties and two major detrimental properties.

One such minor beneficial property is:

>While attuned to the artifact, you have resistance against one damage type of the DM’s choice.

With a 10% chance of rolling this property for an artifact taking 4 minor beneficial properties, there is a 1/10,000 chance an artifact could have the properties proposed in the question. 

**Basically, your player has asked to create one of the most powerful magic items in the universe out of mundane wool and copper.** As you say,

>That is obviously broken.