Do all magnetic fields have the same shape?

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

What is the value of r of the geometric series?

You were told that the amount of time lapsed between consecutive trades on the new york stock exchange followed a normal distribution with a mean of 15 seconds. you were also told that the probability that the time lapsed between two consecutive trades to fall between 16 to 17 seconds was 13%. the probability that the time lapsed between two consecutive trades would fall below 13 seconds was 7%. what is the probability that the time lapsed between two consecutive trades will be between 14 and 15 seconds?