In a solar thermal energy storage prototype, a synthetic thermal oil is heated. During a test run, the temperature of a sample of this oil increases from 25.0∘C25.0^{\circ}\text{C}25.0∘C to 145.0∘C145.0^{\circ}\text{C}145.0∘C as it absorbs 378 kJ of thermal energy. The specific heat capacity of the synthetic oil is 2100 J/kg∘C2100\text{ J/kg}^{\circ}\text{C}2100 J/kg∘C.
Calculate the mass of the thermal oil sample used in this test.