I need help creating an OR function in D15 to only be able to enter a Y or N

I need formulas for D15 and D19

For this exercise, use data validation to: -Use "custom validation" to accept only Y or N in the Preferred Customer input area. Include an input message and an error message -create a dropdown list in the Product Code that allows only values from the Project Lookup table.

If the customer is a preferred customer, then quote the Preferred Price from the Product Lookup Table (name this range), otherwise, quote the regular price.

If either the Product Code or the Preferred Customer indicator is blank, the Price to Quote should also appear to be blank.

"Protect" this worksheet so that a user can change only the input cells (shown in yellow on this page)

Format Painter A Merge & Center Conditional Fo Formatting Clipboard Font Alignment Number St A19 For this exercise, use data validation to: -Use "custom validation" to accept only Y or N in the Preferred Customer input area. Include an input message and an error message -create a dropdown list in the Product Code that allows only 1 2 values from the Project Lookup table. Product Lookup Table Preferred Price Regular Price 140.00 $150.00 $654.00 $5,000.00 $5,468.00 $864.00 $578.00 $549.00 4 If the customer is a preferred customer, then quote the Preferred Price A0001 A0002 A0003 A0004 $600.00 5 from the Product Lookup Table (name this range), otherwise, quote the 6 regular price. $800.00 $525.00 $500.00 575.00$621.00 $825.00 8 If either the Product Code or the Preferred Customer indicator is blank, g the Price to Quote should also appear to be blank. A0007 A0009 A0010 $869.00 $500.00$549.00 11 "Protect" this wor et so that a user can change only the input cells 12 (shown in yellow o nis page) 13 15 16 17 Preferred Customer (Y/N) Product Code Price to Quote! 19 #N/A 21 24 25 StringManipulationVLookup