A small electronics store has begun to advertise in the local newspaper. Before advertising, the long-term average weekly sales were $9,820. A random sample of 50 weeks while the newspaper ads were running gave a sample mean weekly sales of $10,960. Does this indicate that the population mean weekly sales is now more than $9,820? Test at the 5% level of significance. Assume the population standard deviation= $1,580. Compute the z or t value of the sample test statistic.