5(D2-D1) 10(D2-D1) 20(D2-D1) 15(D2-D1)
Answer Discuss in Comment
routine maintenance special maintenance period maintenance recurrent maintenance
20 10 40 30
upper face middle face lower case all of the above
7850kg 2000kg 1000kg 8850kg
light hard soft heavy
urban area semi-urban area rural area all of the above
ashlar random square rubble rubble
2 6 4 3
block glass coloured glass flint glass ground glass
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