[Android Q&A, Help & Troubleshooting] rayooo:
OK, first, excuse my english.

Please update your phone software,before rooting

You'l need this tools> http://yadi.sk/d/PVymQWmm5Sgyo

Extract all packages on your PC desktop

Install mt6577 usb vcom driver for your OS

Connect your cat phone to PC,and install adb driver if needed(when PC ask for driver location, choose folder "usb driver" previously extracted on desktop)

Enable "USB debugging" on your phone Settings> Developer options> Usb debugging.

Now start MtkDroidTools243.exe.After 10-20 sec. the program should recognise the phone as b15.If not,than adb driver is not installed corectly

In mtkdroidtools click on tab "Blocks Map" (pic.1).You need to remember start adress and size of blocks no.9 and no.10 - bootimg and recovery. In my case bootimg- start 01084000 and size-600000: recovery -01684000 size- 600000.I'm pretty much sure,that these adresses are same for everybody,but check anyway

On window "block info" click tab "Create scatter file" , and save file on your desktop (pic.2)

Close Mtkdroidtools for now,and start flashtool.exe from folder Spflashtool 3.1304

Unplug usb cable from PC,shutdown your phone and remove battery

In SPflashtool click on tab "Scatter-loading" and choose previosly created scatter file (pic.3)

Make sure that every tick box under "name" is UNCHECKED and click tab "Read back"

Click twice on tab "add" to create two empty entries (pic.4)

Click twice on first entry,in popup window name the file "boot" and choose location to store this file (pic.5)

In next window, fill start adress and lenght, with start adress and size for "bootimg" from your block info window (pic.6)

Do the same with second entry,but name the file "recovery" and start adress and lenght must match start and size of "recovery" block (pic 7.8)

Now click tab "Read back(F10)" and connect phone to PC with pressed "vol+" and "power" button simultaneously,battery should be disconnected from phone

When Flashtool finished his job(green ring with "OK") ,close it.Put the battery in the phone and power on.

Start mtkdroidtool and when the program recognise the phone, click tab "root,backup recovery"

Check "to choose the boot.img file" and click "Recovery and Boot" button (pic.9)

Here the program asks for "boot" file,created from sp flashtool.When selected, the program asks "to make CWM automatically?",choose "no" and point "recovery" file,created from spflash tool

When done, mtktool asks "install created recovery to phone?" ,choose "no".Note the location of the modified boot and recovery image.

Close the program,shutdown phone, disconnect usb cable from PC and remove battery from phone

Reopen SPflashtools and enter the already created at the beginning scatter file (scatter-loading)

Now check ONLY BOOTIMG and RECOVERY tick boxes (pic.10)

Click twise on bootimg entry and choose modified boot.img file.Do the same with recovery entry

Now click on "Download(F9)" button.There is a message "ALL images are not loaded Correctly, more may cause boot up issue!Do you still want to go on downloading anyway?". Choose "Yes"

Think twise and connect your phone to PC with pressed vol+ key

Spflashtool should upload modified boot and recovery files and show green ring with"OK"

Put battery back and start the phone

When OS load start finaly MTK droid tool and choose tab"root,backup,recovery".Buttons"Backup","SuperUser","Build.prop"and "Delete Cina" should be now active.Click on"Super user"

Now you have rooted cat b15

http://yadi.sk/d/SIFmlyBj6uFJg -pictures