The wording of the problem leaves much to be desired. It does not indicate in which direction is the object’s acceleration. It also fails to mention the presence or absence of friction. In order to cover all conditions, the answer must be a range of values, with the direction changing from zero to ninety degrees.
The range would be: 20 N to 120 N (100 + 20 = 120) starting from zero all the way up to ninety degrees.
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