Data Sufficiency

Here are two data sufficiency questions. Well none of them arent very hard to crack or guess, but can someone detail out the reasoning and the process so the concept is clearer.

Thanks.

Soda concentrate is being added into a soda-making machine in a manufacturing plant. The concentrate is added at a constant rate. At the same time prepared soda is being pumped out of the machine at a constant rate. What is the amount of soda per minute is being pumped out in 15 minutes?

(1) The soda machine has a capacity to hold 1000 gallons of water.

(2) 25 gallons of concentrate is added every minute and total volume of liquid in the machine is reduced by 75 gallons per minute.
Ans B

In a cookie-eating contest, there are 200 cookies provided to each contestant. Both start at the same time. Contestant A wins the contest by eating 20 more cookies than Contestant B. How many cookies did the winner eat altogether?

(1) Contestant A ate his cookies at a constant rate of 20 cookies per minute and Contestant B ate her cookies at a constant rate of 15 cookies per minute.

(2) Contestant A is younger than Contestant B.

Ans A