Answer:

Explanation:
John spends $2.75 on donuts for his office employees every weekday, so he spends 5 * $2.75 = $<<5*2.75=13.75>>13.75 on donuts for his office employees throughout the week.
He also spends $12.99 on donuts on Sunday mornings, so in total he spends $13.75 + $12.99 = $<<13.75+12.99=26.74>>26.74 on donuts throughout the week. Answer: \boxed{26.74}.