Answer:
Unfulfilled Expectations
Explanation:
Kevin expects to get $100 dollars at the end of the week and therefore has based his expenses on his expected paycheck.
Unfulfilled expectations could lead to anger, upset and frustrations.
The psychology of expectations made him pinned his hopes for expecting his full earnings on fulfilled expectations; the reason he's upset even after he found out that his colleagues earned $20 little than he earned.
Also, he must have felt cheated after finding out that his paycheck was less than $100