It is now believed that protones and neutrons (which constitute nuclei of ordinary matter) are themselves built out of more elementary.units called quarks. A proton and a neutron consist of three quarks each. Two types of quarks, and so called 'up' quark (denoted by u) of change + (2/3)u and the 'down' quark (denoted by d) of charge (-1/3)e, together with electrons build up ordinary matter (Quarkes of other types have also been found which give rise to different unusual varities of matter) Suggest a a possible quark composition of a proton and neutron.