The buoyant force of a fluid on an object is equal to the weight of fluid that is displaced by the object. To calculate the buoyant force, we need to subtract the apparent weight of the object in the fluid from its true weight in air.
In this case, the true weight of the metal block in air is 3.7 N, and its apparent weight in the vegetable oil is 1.6 N. So, the buoyant force of the vegetable oil on the metal block would be:
Buoyant force = True weight - Apparent weight
= 3.7 N - 1.6 N
= 2.1 N
So, the buoyant force of the vegetable oil on the metal block is 2.1 N.