A company makes and sells product X and product Y. Twice as many units of product Y are made and sold as that of product X. Each unit of product X makes a contribution of £10 and each unit of product Y makes a contribution of £4. Fixed costs are £90,000.

What is the total number of units which must be made and sold to make a profit of £45,000?
(a) 7,500
(b) 22,500
(c) 15,000
(d) 16,875