Sheila has been given 5 minutes to solve 20 problems. What is the minimum rate Sheila can work in order to finish in time?
A:1 problem per minute

B: 2 problems per minute

C: 4 problems per minute

D:5 problems per minute

The table below shows the approximate masses of a dust particle and a grain of pollen. dust particle 0.000000778 g grain of pollen 0.00000000155 g the mass of a dust particle can be estimated and written in the form a × 10^b, where a = 8 and b = the mass of a grain of pollen can be estimated and written in the form a × 10^b, where a = 2 and b = based on the estimates, the mass of a dust particle is approximately blank times larger than the mass of a grain of pollen.