When operating at design conditions (smooth exit to sea-level pressure), a rocket engine has a thrust of

Question:

When operating at design conditions (smooth exit to sea-level pressure), a rocket engine has a thrust of 1 million lbf. The chamber pressure and temperature are 600 lbf/in2 absolute and 4000°R, respectively. The exhaust gases approximate k = 1.38 with a molecular weight of 26. Estimate
(a) The exit Mach number and
(b) The throat diameter.