If the number of photos ordered is more than 99 and fewer than 200 each photo cost 0.17 and there is a $4.50 shipping fee of 200 or more photos are ordered each photo cost 0.15 and there's no shipping fee what is the piecewise define function that expresses the cost of the order in terms of the number of photos ordered

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.