An air-filled toroidal solenoid has a mean radius of 15.1cm and a cross-sectional area of 4.95cm2 (see the figure). The current flowing through it is 12.5A , and it is desired that the energy stored within the solenoid be at least 0.394J . What is the least number of turns that the winding must have? Express your answer numerically, as a whole number, to three significant figures.