Tamarisks World Toy Shop is an on-line toy store specializing in hand-made stuffed animals. Tamarisks World sold 4000 Donny the Dragon stuffed toys during April and 6000 during May. Shipping costs for the two months were $12600 and $17200 respectively. Using these two months data, the shipping cost function is best estimated as

($2.30 number of toys sold) + $3400.

($3.15 number of toys sold) + $2980.

($0.50 number of toys sold) + $10600.

($2.10 number of toys sold) + $73600.