2.556 billion growing at a rate of 1.68% how long until it reaches 2.78 billion

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b

Which one is the correct answer, and why?

For the feasibility region shown below find the maximum value of the function p=3x+2y