PLS HELP ME I ADDED MORE POINTS

The level of co2 emissions, f(x), in metric tons, from the town of fairfax x years after they started recording is shown in the table below. x 2 4 6 8 10 f(x) 26,460 29,172.15 32,162.29 35,458.93 39,093.47 select the true statement.

What is the the greatest common factor ?

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)