i'll thumbs up if correct answer and u explain properly

A company sells ten variants of a product. To make postponement possible so the inventories can be kept in component form the company needs to introduce commonality in the product. Currently, total cost for each device is $900. Introducing commonality will increase the cost to $990. Weekly demand for one of the ten variants (P1) is normally distributed, with a mean of 800 and a standard deviation of 210. Each of the other nine variants (P2 to P10) has a weekly demand of 25 with a standard deviation of 20. The company aims to provide a 90 percent level of service. Lead time for parts is 3 weeks. The company manages all inventories using a continuous review policy and incurs an annual holding cost of 15%.

What is the standard deviation of the aggregate weekly demand?

		128
		182
		None of the options
		218
		281

A company sells ten variants of a product. To make postponement possible so the inventories can be kept in component form the company needs to introduce commonality in the product. Currently, total cost for each device is $900. Introducing commonality will increase the cost to $990. Weekly demand for one of the ten variants (P1) is normally distributed, with a mean of 800 and a standard deviation of 210. Each of the other nine variants (P2 to P10) has a weekly demand of 25 with a standard deviation of 20. The company aims to provide a 90 percent level of service. Lead time for parts is 3 weeks. The company manages all inventories using a continuous review policy and incurs an annual holding cost of 15%.

What is the average of aggregate weekly demand?

		None of the options
		2150
		1025
		1205
		1250

A company sells ten variants of a product. To make postponement possible so the inventories can be kept in component form the company needs to introduce commonality in the product. Currently, total cost for each device is $900. Introducing commonality will increase the cost to $990. Weekly demand for one of the ten variants (P1) is normally distributed, with a mean of 800 and a standard deviation of 210. Each of the other nine variants (P2 to P10) has a weekly demand of 25 with a standard deviation of 20. The company aims to provide a 90 percent level of service. Lead time for parts is 3 weeks. The company manages all inventories using a continuous review policy and incurs an annual holding cost of 15%.

A new analysis of historical data shows that the aggregate weekly demand (P1 to P10) is 1100. What is the average of aggregate demand over lead time?

		3300
		3200
		3000
		3100
		None of the options

A company sells ten variants of a product. To make postponement possible so the inventories can be kept in component form the company needs to introduce commonality in the product. Currently, total cost for each device is $900. Introducing commonality will increase the cost to $990. Weekly demand for one of the ten variants (P1) is normally distributed, with a mean of 800 and a standard deviation of 210. Each of the other nine variants (P2 to P10) has a weekly demand of 25 with a standard deviation of 20. The company aims to provide a 90 percent level of service. Lead time for parts is 3 weeks. The company manages all inventories using a continuous review policy and incurs an annual holding cost of 15%.

The new analysis also shows that the standard deviation of the aggregate weekly demand is 220. What is the standard deviation of the aggregate demand over lead time?

		318
		831
		381
		138
		None of the options

plz answer correctly and explain answer