Hello can someone please help me with this question and show all working so I can follow along please

a) The mass of a proton is 1.6725 x 10-27 kg. The mass of a neutron is 1.6748 x 10-27 kg. The mass of an electron is 9.1091 x 10 3 kg. If a single Boron atom contains 4 protons, 4 neutrons and 4 elec- trons, how much do 6.02 x 1025 Boron atoms weigh? b) 21% of a 270 kg cement mixture is sand. How much sand must be added to build a new mixture weighing more than 270 kg which contains 25% sand? c) A can of tennis balls fits exactly 3 as shown in the diagram below. Calculate the radius of each tennis ball and hence determine the volume of the can in cubic centimetres. 37 cm d) The total resistance of two parallel resistors is found by evaluating the expression: R1R2 RTOTAL = R1 + R2 If the total resistance, RTOTAL is 1200 and R1 is 2400, what will be the value of R2? e) Divide 8 x 10-3 into the ratio 2:3:5