LCM – 2 ways use either weight of popcorn or price. I assume no calculator hence using weight will be easier
LCM of 150g and 200g will be 600g.
150 * 4 = 600g
200g* 3 = 600g
7.90*4 = 31.60 which is more expensive than 9.90*3 hence option B more value for money