Task: Question Answering
Input (English): Problem: company x provides bottled water to its employees in 10 liter bottles, $ 2 each. at least how many 10 l bottles must company x buy monthly, so that new contract with $ 50 fixed monthly rate and $ 1 for 50 l bottle each paid off ? ( assume that no other costs apply )
Options: a. 28, b. 29, c. 30, d. 31, e. 32
Output (English): a