In a surface mine blast, the peak particle velocity (V in mm/s) is estimated from the equation $${\text{V}} = 120{\left( {\sqrt {{\text{SD}}} } \right)^{ - 1.0}},$$     where SD is square root scaled distance. If at a distance of 100 m from the blast site the permissible peak particle velocity is 25 mm/s, the maximum charge per delay in kg is