Palm oil, used for food, various consumer goods, and biofuels, is produced from the oil palm tree. oil palm plantations in malaysia account for 13% of the land area, which is up from 1% in 1974. the biofuel potential of palm oil could mean an even further increase in the acreage of rainforest converted to oil palm plantations. one of the indicators used to monitor the environmental impacts of the oil palm plantations is the amount of n2o
emitted from the soil. a published report1 measured the nitrogen released from the soil in a oil palm plantation and a rainforest. the data is given in the table. note that the mean flux value of nitrogen from soil is expressed as the mean plus or minus one standard deviation.

rainforest oil palm plantation

mean flux of nitrogen
from soil (mg n/m^2 *h) 0.036+-0.041 0.051+-0.040

# of measurements 89 101

calculate the value to compare these two means. assume the population standard deviation for each data set is the same.

at which of the confidence levels are the results different?
(options: 99.8%, 99.9%, 98%, 99%, 95%, 90%)

my work thus far:
i calculated the s pooled and i got an equation, calculating the t calc, but i do not know how to incorporate the uncertain values into the t calc:

equation: