From the chocolate-bar schedule, total utility is 50 utils at both 4 and 5 units, and 46 utils at 6 units. The marginal utility of the 6th unit is:

1. $MU_6 = TU_6 - TU_5 = 46 - 50 = -4$ utils. 2. The negative value shows the 6th unit yields disutility and reduces total satisfaction. 3. Zero is the MU of the 5th unit, +4 ignores the sign, and +46 confuses MU with TU, so all are wrong. _Source: ICAI BoS CA Foundation Paper 4 Business Economics, Ch 2 Unit II "Theory of Consumer Behaviour", p.5_