576
.xls
application/vnd.ms-excel
.xlsx
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.ppt
application/vnd.ms-powerpoint
.pptx
application/vnd.openxmlformats-officedocument.presentationml.presentation
And one of those you have listed is wrong:
.docx
application/vnd.openxmlformats-officedocument.wordprocessingml.document