109) A business has 7 locations, to chose from and wishes to rank only the top 3 locations. How many different ways can this be done?

A) 120
B) 840
C) 210
D) 5,040
E) 32

step-by-step explanation: a reaction is first order. if the initial reactant concentration is 0.0200 m, and 25.0 days later the concentration is 6.25 x 10-4 m, then its half-life is:

i think it would be 42cm

my guess would be b and d, but i didn’t actually get out the pen and paper. lol