CVP analysis

Hi my Dear tutor,? have a question.

Product—————————–A——B———-C
Sales—————————-1794–3740—2950
production cost of sales—1242—-2860—1888
gross profit——————–552——880—-1062

non production overheads–460—-770—-767
net profit————————–92——110—-295
sales units——————-1150——–2200—2360

fixed production overheads are absorbed at a rate of 0.30 per unit for each product.Non-production overheads include certain costs that vary with activity at a rate of 10% of sales value.

calculate,based on the current mix of sales, the sales required of each product in order to generate a total contribution of 3750 per annum

Solution

Total sales————————————————————8484
Variable production costs:
Total production costs(1242+2860+1888)–5990
Fixed production cost(5710 units *0.30)—(1713)
Variable non-production cost(8484*10%)—(848,4)
total contribution—————————————————-3358,6

My question here is that

Sales required 8484*3750/3358,6=9473

Why i multiply 8484 by 3750 and dividing 3358,6?i have two total contribution 3750 and 3358,6 and never faced any formula like that .

could u explain?