#### Answer

3.5

#### Work Step by Step

We are given that the formula $R=log(\frac{a}{T})+B$ can be used to find the intensity R of an earthquake on the Richter scale (where a is the amplitude in micrometers, T is the time in seconds between waves, and B is a constant).
In this case, $a= 150$, $T=3.6$, and $B=1.9$.
We can plug in these values to find R. Recall that $log(\frac{a}{T})$ is written in the form of the common logarithm and has a base of 10.
$R=log(\frac{150}{3.6})+1.9=log(41.67)+1.9=1.6+1.9=3.5$