Problem solving, either i am retarded or this problem is really hard, Help me please

A patient is given a nasogastric solution containing 40 grams per liter each of fat, carbohydrate
and protein. Calculate the total number of calories is receiving if he is fed 2.5 liters of the
solution daily.

First you should know the amount of calories contributed by per g of fat, protein and carbohydrate, they are respectively 9, 4 and 4 cal/g
So Fat 40 g x 9 = 360 cal
protein 40 xs 4 =160
and carbohydrtes 40 x4 =160
Total calories per liter = 360+ 160 +160 =680 cal/L
so for 2.5 L, it will be 2.5*680 = 1700 cal/day

There you have it.

100g