I installed Windows 10 on a 60GB SSD (/dev/sdc in Ubuntu) in my computer, then installed Ubuntu 15.10 on a 120GB SSD (/dev/sda in Ubuntu) in my computer. GRUB boots straight into Ubuntu. When I hold shift upon startup and see GRUB, there is no Windows 10 entry.
I'd like the GRUB menu to show every time, and I'd like a Windows 10 entry in GRUB that'll boot into it.