7. You have two pairs of plaintext-ciphertext:(whatarethese, FEGUQQJZTNHC)and(whatarethose, FEGUQQJZTPKC).both encrypted by the same method and with the same key. Give examples of two ciphers that could nothave been used in this communication. Explain.

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]

Find the minimum film thickness for a journal bearing with the data below. shaft diameter, d-50 mm, clearance ratio, cdratio? 0.001, shaft speed, n 2000 rpm; bearing length. i 200 mm; eccentricity ration, ? -0.55. ( note, cdratio-ca/d) the minimum film thickness is um

For a gate width of 2 m into the paper, determine the force required to hold the gate abc at its location.