revenue with equations

please sir help me
The following information relates to questions 24 and 25:
A company has established the following selling price, costs and revenue equations for one of its products:
Selling price (£ per unit) = 50 – 0·025Q
Marginal revenue (£ per unit) = 50 – 0·05Q
Total costs per month (£) = 2,000 + 15Q
Q represents the number of units produced and sold per month.
24 At what selling price will monthly profits be maximised?
A £15·00
B £17·50
C £25·00
D £32·50
25 What would be the monthly profit if the selling price per unit was set at £20?
A £1,000
B £4,000
C £6,000
D £12,000