The inverse of the matrix $$\left[ {\matrix{ {3 + 2i} & i \cr { - i} & {3 - 2i} \cr } } \right]$$ is

Ion concentrations obtained for a groundwater sample (having pH=8.1) are given below.

Ion	$$Ca^{2+}$$	$$Mg^{2+}$$	$$Na^+$$	$$HCO_3^-$$	$$SO_4^{2-}$$	$$Cl^{-}$$
Ionconcentration(mg/L)	100	6	15	250	45	39
Atomic Weight	Ca=40	Mg=24	Na=23	H=1,C=12,O=16	S=32,O=16	Cl=35.5

Total hardness (mg/L as $$CaCO_3$$) present in the above water sample is

Ion concentrations obtained for a groundwater sample (having pH=8.1) are given below.

Ion	$$Ca^{2+}$$	$$Mg^{2+}$$	$$Na^+$$	$$HCO_3^-$$	$$SO_4^{2-}$$	$$Cl^{-}$$
Ionconcentration(mg/L)	100	6	15	250	45	39
Atomic Weight	Ca=40	Mg=24	Na=23	H=1,C=12,O=16	S=32,O=16	Cl=35.5

Carbonate hardness (mg/L as $$CaCO_3$$) present in the above water sample is

The moisture holding capacity of the soil in a 100 hectare farm is 18 cm/m. the field is to be irrigated when 50 percent of the available moisture in the root zone is depleted. The irrigation water is to be supplied by a pump working for 10hours a day, and water application efficiency is 75%. Details of crops planned for cultivation are as follows:

Crop	Root zone depth (m)	Peak rate of moisture use(mm/day)
X	1.0	5.0
Y	0.8	4.0

The area of crop Y that can be irrigated when the available capacity of irrigation system is 40 liters/sec is