3. An investment of Rs. 100 lakhs is to be made for construction of a plant, which will take two years to start production. The annual profit from the operation of the plant is Rs. 20 lakhs. What will be the pay back time?
5. According to six-tenths-factor rule, if the cost of a given unit at one capacity is known, then the cost of similar unit with '' times the capacity of the first unit is approximately equal to __________ times the cost of the initial unit.
10. Metallic recuperators are not used for waste heat recovery, if the hot flue gas temperature is above __________ °C, because corrosion prevails at higher temperatures.