Pool battery samples before calculating a test

A consumer association tests a battery type claimed to have mean lifetime 150 hours. A random sample of 70 lifetimes gives $\sum x=10317$, $\sum x^2=1540231$. Test $H_0:\mu=150$ against $H_1:\mu<150$: find the p-value and explain it in context.

A second random sample of 50 lifetimes gives $\sum y=7331$, $\sum y^2=1100565$. Combine the samples into one and test the same hypotheses at 10%.