Use the cost table below to find the following marginal costs.

Output quantity	Total variable cost	Total fixed cost	Total cost
20	80	60	140
40	140	60	200
60	210	60	270
80	300	60	360
100	420	60	480
120	600	60	660
140	840	60	900

What is the marginal cost when output is60?$ What is the marginal cost when output is100?$ What is the marginal cost when output is120?$