What is the recursive rule for this geometric sequence? 7, 21, 63, 189, …

a. a1=7; an=3⋅an−1

b. a1=7; an=13⋅an−1

c. a1=21; an=7⋅an−1

d. a1=3; an=7⋅an−1

ppplllease

The price of a box of 15 cloud markers is $12.70. the price of a box of 42 cloud markers is $31.60. all prices are without tax, and the price of the packaging is the same for any size. how much would 50 cloud markers in a box cost? write an equation which will tell the price p for the number n markers in the box.