(a)[2]
Company $A$ charges $\$0.50$ per box, together with a fixed charge of $\$125$. Company $B$ charges only a fixed amount of $\$350$. Find how many boxes are moved when Company $A$ and Company $B$ charge the same.
(b)[2]
The van’s maximum load is exactly $770\,\text{kg}$. It carries boxes with mass $4\,\text{kg}$ each, correct to the nearest kilogram. Find the upper bound for the number of boxes this van can carry.
(c)[3]
A lorry is loaded with boxes in three categories, $S$, $M$ and $L$. The ratio of the numbers of $S$ boxes to $M$ boxes is $2 : 7$. The ratio of the numbers of $S$ boxes to $L$ boxes is $5 : 4$. There are $72$ boxes of size $L$ in the lorry. Find the total number of boxes in the lorry.