Averages of daily minimum and maximum temperatures for a week.

The minimum temperatures are:
Monday: $21^\circ$
Tuesday: $19^\circ$
Wednesday: $16^\circ$
Thursday: $18^\circ$
Friday: $17^\circ$
Saturday: $16^\circ$
Sunday: $22^\circ$

The minimum average temperature for the week is $\boxed{\text{}18.43^\circ\text{}}$

B)

The maximum temperatures are:
Monday: $38^\circ$
Tuesday: $30^\circ$
Wednesday: $30^\circ$
Thursday: $37^\circ$
Friday: $34^\circ$
Saturday: $31^\circ$
Sunday: $39^\circ$

The maximum average temperature for the week is $\boxed{\text{}34.14^\circ\text{}}$