Break Even point

John sells pushchairs on eBay. He buys the pushchair from China at a wholesale price of £350 and resells them for £450. He also needs to store them before they are buying dispatched so he rented a garage space for £800 a month. a. What is the equation to calculate the profit? b. How many pushchairs does John need to sell to break even? c. If John were to sell 23 pushchairs, what would be his profit/loss? (a) Selling price - Cost (£450-£350) = £100 profit = £100 fixed cost = 800 per month (b) to break even , sales = costs , where there is no profit or loss. units to be sold to break even in unit = fixed costs/contribution per unit = 800/100= 8 units (c) 23*450 per units = £10,300 as sales revenue 10,300-8050( 350 costs per unit of pushchairs * 23) = £2,250. Sir please, is this correct ? but answers from the book differes