Wildhorses World Toy Shop is an on-line toy store specializing in hand-made stuffed animals. Wildhorses World sold 4000 Donny the Dragon stuffed toys during April and 6000 during May. Shipping costs for the two months were $12000 and $16200 respectively. Using these two months data, the shipping cost function is best estimated as

($0.50 number of toys sold) + $10000.

($2.10 number of toys sold) + $3600.

($3.00 number of toys sold) + $2820.

($2.00 number of toys sold) + $70000.