To determine the density of grains, a student uses a 50ml beaker graded by 5ml increments and a scale with 1g absolute uncertainty. The measurement of the volume results in 3 full beakers and 1 beaker filled up to 30ml. Measured mass of a plastic container with all the grains is 185 grams; measured mass of the same container without grains is 65 grams. What is the mass of the grains