2355 ml
First, convert 211 lbs to kg by multiplying by 0.453592
211 lb * 0.453592 kg/lb = 95.70791 kg
Now find the LD50 dose
95.70791 kg * 150 mg/kg = 14356 mg
Now figure out how many mg/ml in the drink
0.61% * 1 = 0.0061 * 1 = 0.0061 = 6.1 mg/ml
Finally, divide the LD50 dose by the concentration.
14356 mg / 6.1 mg/ml = 2354.918 ml
Rounding to the nearest ml, the LD50 dose will be 2355 ml.