4 (a) Discuss the essential features of Differential Piece Rate System of Wage Payment. What are the advantages and disadvantages of this system?: (b)(Labour cost per piece at 5% intervals between 65% and 125% efficiency) In a manufacturing unit, a multiple piece rate plan is operated as under: (i) Basic piece rate up to 85% efficiency: (ii) 115% basic piece rate between 90% and 100% efficiency; (ii) 125% basic piece rate above 100% efficiency. The workers are eligible for a "Guaranteed Day Rate which is equal to 75% efficiency and the piece rate is Rs. 2.00 per piece. Compute the labour cost per piece at 5% intervals between 65% and 125% efficiency, assuming that at 100% efficiency 60 pieces are produced per day