What is the state of the system at time t2?

For the purposes of this problem, 10 kg of air in a 10-m3 rigid airtight tank are assumed to have only two independent properties, A and B. At time t1 = 0, measurements yield that A = 12 and B = 14, whereas at time t2 = 5 h the same measurements yield A = 10 and B = 14.

(a)  What is the system in this problem?

(b) What are the values of the amounts of constituents and the parameters? What are the ranges of these values?

(c)  What is the state of the system at time t1?

(b)  What is the state of the system at time t2?