Q64

A transporter receives the same number of orders each day. Currently, he has some pending orders (backlog) to be shipped. If he uses $7$ trucks, then at the end of the $4^{th}$ day he can clear all the orders. Alternatively, if he uses only $3$ trucks, then all the orders are cleared at the end of the $10^{th}$ day. What is the minimum number of trucks required so that there will be no pending order at the end of $5^{th}$ day?