One sample t-test

In a research study, it was expected that the mean value of a data set would be 1200. The researchers thought the initial number they got was only a theoretical value. They suspected the actual mean might be higher because of some unknown factors. To validate their suspicion, they took a sample of 40 data points and found the sample mean to be 1220, with a sample standard deviation of 40.9.

Their hypotheses were:

$H_0:\mu=300\\H_1:\mu>300$

Considering these data points, what would be the t-value?