Suppose a and b are independent. if p (a) = 0.7 and p (b) = 0.8, what is p (aΩb)

Given events A and B are mutually inclusive ... P (A or B) if P (A) = 0.4 P (B) = 0.7 P (AΩB) = 0.3I know I have to use the addition rule and the fomulanecessary is P (A or B) = P (A) + P (B) - P (AΩB) I am using the greek symbol as intersection not even sure ifit is appropriate to use that symbol as intersection. Do I just plug the numbers in and get 0.8 as myprobability?