(i) The minimum number of pollen grains that must have been involved are 240, as 240 viable seeds are formed. This is because each pollen grain contains 2 male gametes, out of which one fuses with egg forming zygote that gives rise to seeds.
(ii) The minimum number of ovules would also have been 240, as 240 viable seeds are formed. After fertilisation the ovule turns into seeds.
(iii) 240 megaspore mother cells were involved. They undergo meiotic division to form 4 haploid megaspore. Out of them only 1 becomes functional megaspore and rest 3 degenerate.
(iv) The minimum number of microspore mother cells in the above ease would be 60. This is because each microscope mother cell gives rise to 4 microspores. Thus, to obtain 240 riHcrospores, 60 microspore mother cells are required.
(v) The number of male gametes involved would be 240. Each male gamete fuses with one egg nuclei to form zygote that gives rise to seed.