By how many litres a day did the cooperative's total summer collection fall short of its winter collection?

Explanation

1. 01

   Winter total: $1{,}200 + 800 + 1{,}500 + 600 + 900 = 5{,}000$ litres.

2. 02

   Summer total: $840 + 720 + 1{,}125 + 570 + 810 = 4{,}065$ litres.

3. 03

   Shortfall: $5{,}000 - 4{,}065 = 935$ litres a day.