(iii) According to the Principle of duality, the Boolean equation
(P + Qꞌ) • R • 1 = P • R + Qꞌ • R will be equivalent to:
(a) P • Qꞌ + R + 1 = (P + R) • (Qꞌ + R)
(b) P • Qꞌ + R + 0 = (P + R) • (Qꞌ + R)
(c) Pꞌ • Q + R + 1 = (Pꞌ • Rꞌ) • (Q + Rꞌ)
(d) P • Qꞌ + R • 0 = (P + R) • (Qꞌ + R)

Solution

(b) P • Qꞌ + R + 0 = (P + R) • (Qꞌ + R)