Answer:
Standard deviation     Percentage from table   Number of bags out of 600
-2 to -1 (47 to 48.5 lbs) Â Â 13.6% Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 82
-1 to 0 (48.5 Â to 50 lbs) Â Â 34.1% Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 205
0 to +1 (50 Â to 51.5 lbs) Â Â 34.1% Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 205
+1 to +2 (51.5 Â to 53 lbs) Â Â 13.6% Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 82
Step-by-step explanation
standard deviation is 1.5 lbs and mean is 50 lb, then:
mean - 2*standard deviation  = 47 lb
mean - 0*standard deviation  = 50 lb
mean + 2*standard deviation  = 53 lb
0.341*600 = 205
0.136*600 = 82
The percentages are shown in the figure attached.