In a room-and-pillar stope, bench blasting is conducted using ANFO having density of 800 kg/m<sup>3</sup>. The specific gravity of rock is 2.5, hole diameter is 100 mm and spacing to burden ratio is 1.3. The charge length of each blast hole is 80% of the hole length. For a desired powder factor of 0.48 kg/tonne, the spacing and burden of the blast pattern in m respectively are

Correct Answer: 2.3, 1.8