4. Let a, b, u, v, and z be five vectors of the same size. Suppose that: (a) u is a linear combination of a and b with coefficients p and p2, (b) v is a linear combination of a and b with coefficients q and 92, and (c) z is a linear combination of u and v with coefficients a and a2. Show that z is a linear combination of a and b. (Follow the following steps) Step 1: Write the meaning of the statement in (a). Step 2: Write the meaning of the statement in (b). Step 3: Write the meaning of the statement in (c). Step 4: Express z in terms of a and b.