Firm $A$ is a successful firm and thus the going concern is applied. Customer B requests a change of credit policy from cash only to net $30$ days. Assuming the price per unit is $$50,$ the variable cost per unit is $$30,$ the current quantity sold per month is $100,$ the quantity sold under the new policy per month is $120,$ and the monthly required return is $2\%,$ calculate the cost of switch.

$$5,000$

$$5,600$

$$4,400$

$$5,400$

$$6,000$