Crops are grown in a field having soil, which has field capacity of $30\%$ and permanent wilting point of $13\%.$ The effective depth of root zone is $80\ cm$. Irrigation water is supplied when the average soil moisture drops to $20\%.$ Consider density of the soil as $1500\ kg/m^3$ and density of water as $1000\ kg/m^3$. If the daily consumptive use of water for the crops is $2\ mm$, the frequency of irrigating the crops (in days), is

1. $7$
2. $10$
3. $11$
4. $13$

Answer: