Answer:
In this question, we are using 2016 federal tax rate schedule for married filing jointly.
(a) Federal tax they owe = $29,517.50 + 28%($190,500 - $151,900)
= $29,517.50 + $10,808
= $40,325.5
(b) Their Average tax rate =

= 0.2116
= 21.16%
(c) Their effective tax rate =

= 0.1828
= 18.28%
(d) Their current marginal tax rate is 28%