I give you the formula:
 \frac{(9.0 x10^{9})*(100 x^{-6})* (150 x^{-6)} }{(150cm)^{2}  }
i give you the solution but solve this in your scientific calculator because i can not brought my calculator so u have an idea to solve it... if u see like that  10^{9} just press EXP if negative like milli or micro just press EXP-6 or EXP-3 depends what have given .. like for example:  9.0*10^{9} or 9.0x 10^{9}  so use this 9.0 Press: EXP and 9 and click multiply the 100micro same procces press EXP-6 and so on so for .. remember the cm is  ^{2} and this is the formula: