Compute the percent markup on selling price

Question

Response to the following problem:

An Apple Computer Center sells computers for $1,258.60. Assuming the computers cost $10,788 per dozen, find for each computer the

(a) dollar markup,

(b) percent markup on cost, and

(c) percent markup on selling price (nearest hundredth percent).

Prove (b) and (c) of the above problem using the equivalent formulas.