Heat,work, thermal efficiency problems

[mocha1209]

This is the question that I can't really answer

1. A cycle looks like an ellipse in the T-S diagram. The maximum and minimum temperatures are 1000K and 400K. The maximum and minimum entropies are 0.705 KJ/K and 0.235 Kj/K. Determine
a. the heat added per cycle, b. the work produced per cycle, c. The thermal efficiency of the cycle.

I'm trying to answer this question but I am pretty confused about having the minimum and maximum values. I don't even know what formua to use.

There is another question:

2. There are added 20 BTU to 5lb of carbon dioxide at constant volume. The initial temperature is 90F. (CV= 0.1565 Btu/lb-R) Determine. a the final temperature b. the change of enthalphy. c. The change of internal energy.

Im trying to answer this but I am getting confused about the BTU added to lb. I don't know how could I get BTU from lb to have it added.

Please help me out. I really need your help. This is a make or break of my grades. Thank you needed your response.

 

[SteamKing]

In problem 2) it's 20 BTU of heat added to 5 lbs of CO2. It is analogous to adding 20 kJ of heat to 5 kg of CO2.